Field of the Invention
The present invention relates to a wireless communication technique of transmitting data in a plurality of different antenna directions.
Description of the Related Art
A technique of performing wireless communication in frequency bands such as a millimeter wave band/submillimeter wave band is being extensively examined. Since a wide bandwidth can be secured in a frequency band like this, high-speed wireless transmission is possible. Generally, as the frequency increases, high-speed communication becomes possible by securing a wide bandwidth, but the frequency gradually gains a property close to that of light, so the straightness increases. That is, when using a frequency band such as a millimeter wave band, if an obstacle exists in the propagation direction of a radio wave, the communication quality of a communication path pertaining to the propagation direction significantly deteriorates.
On the other hand, International Publication No. 2012/131924 describes a technique of transmitting data from a transmitting station to a receiving station by using a predetermined communication path, and, if the transmitting station cannot receive any acknowledgement from the receiving station, retransmitting the same data by using another communication path.
In this technique described in International Publication No. 2012/131924, if no error occurs in a communication path used in normal operation, other communication paths are not used. Therefore, the states of the other communication paths cannot be known unless an error occurs. In wireless communication, the state of a communication channel often changes. Accordingly, even when a plurality of communication paths having a high communication quality are prepared in advance, while no problem arises in communication quality of one communication path in use, the state of another communication path sometimes changes such that no satisfactory communication quality can be obtained. In this case, if a communication error occurs in the communication path in use and the communication path is switched to another communication path, an error may occur in this communication path as the switching destination.
The present invention provides a communication method capable of monitoring the states of a plurality of set communication paths during communication.